Dec. 20, 2010 -- New research suggests that one out of every 200 patients being treated with gastric acid-suppressive drugs for heartburn and other conditions may develop pneumonia.

Researchers led by Chun-Sick Eom, MD, MPH, from Seoul National University Hospital in South Korea, conducted a review of studies published between 1985 and 2009, looking at the use of gastric acid-suppressive drugs and the risk of developing pneumonia.

Acid Suppressives Strongly Linked to Pneumonia

The researchers found a significant association between the use of one class of gastric acid suppressive, called proton pump inhibitors, and pneumonia. Eom and his colleagues also found a dose-response relationship between proton pump inhibitors and risk of pneumonia, meaning the more acid suppressive a patient took, the higher the risk of developing pneumonia. Examples of proton pump inhibitors include Aciphex, Nexium, Prevacid, Prilosec, Protonix, and Zegerid.

The researchers also found a strong association between the use of another class, histamine 2-receptor antagonists, and pneumonia. Examples of histamine 2 receptor antagonists include Axid, Pepcid, Tagamet, and Zantac.

The results are published in the Dec. 20 issue of the Canadian Medical Association Journal.

Forty percent to 70% of hospitalized patients receive acid suppressive medication. The researchers say frequent use of these drugs may be contributing to hospital-acquired pneumonia illnesses and deaths. The findings suggest that doctors should exercise caution when prescribing these acid suppressives, particularly among patients at high risk for developing pneumonia.

Biological Explanations

There may be several reasons as to why acid suppressives may have this association with pneumonia, Eom and his team report. Acid-suppressive drugs may increase the risk for pneumonia by blocking gastric acid, which could lead to bacteria overgrowth in the upper gastrointestinal tract that may travel to the lungs. It's also possible the acid-suppressive medication inhibits immune cells, reducing their ability to fight off bacteria and infection.

Acid-suppressive drugs are the second most commonly sold and used medication worldwide, totaling more than $26 billion in sales in 2005 in the U.S. They are prescribed to treat conditions such as heartburn, gastroesophageal reflux disease, and ulcers. Previous studies have examined a possible link between these drugs and pneumonia in the past, but the results have been mixed.

"Several previous studies have shown that treatment with acid-suppressive drugs might be associated with an increased risk of respiratory tract infections and community-acquired pneumonia in adults and children,” Eom and his colleagues wrote. "Given the widespread use of proton pump inhibitors and histamine 2-receptor antagonists, clarifying the potential impact of acid-suppressive therapy on the risk of pneumonia is of great importance to public health."